The present invention relates to optical fiber connector devices and methods and, more particularly, relates to such devices and methods having springs to increase the contact force at the contact face in fiber to fiber joints to effect exceptional optical connections.
Conventional fiber optic connectors typically employ precision ferrules aligned with sleeves to provide alignment in fiber to fiber optical connections. Ends of optical fibers to be optically connected are each equipped with a ferrule. The ferrules are typically cylindrical, with an inner, longitudinal cylindrical void to accommodate a single optic fiber end with minimum tolerance. The optic fiber end fills the cylindrical void of the ferrule and is secured in place in the ferrule by an adhesive or other means. The sleeve has a void for accommodating and retaining ferrules, for example, two ferrules, in particular alignment. Because the ferrules accommodate the optic fiber ends, the optic fiber end faces are selectively alignable for optical connectivity by selectively positioning the ferrules with respect to each other. For example, two ferrules may be positioned within the sleeve, end to end, in order to position the optic fibers contained by the ferrules end face to end face in optical alignment and connection.
Ferrules containing optic fiber ends may be spring loaded to force the ferrules, and thus the optic fibers, to maintain desirable end face contact for a stable optical connection. In such contact, the fiber end faces elastically deform to make a desirable fiber optic to fiber optic connection. The fiber and ferrule end faces are precisely polished to control the fiber protrusion from the ferrule, for example, to control the protrusion to within tolerances of+/-50 nanometers.
Disadvantages of ferrule and sleeve connectors for optic fibers include the costs of the components, the precision required of the components, and the complex installation process. Relative to costs for copper connections, these disadvantages have made costs for fiber optic connections higher and, in many instances, use of fiber optics in lieu of copper wires economically unfeasible.
Conventional index matching gel is sometimes employed with fiber optic connectors. In connector designs employing the gel, the gel minimizes reflection in order to provide good optical connection. The use of index matching gel in fiber optic connections, however, has certain limitations. Furthermore, index matching gels are costly. Their use with conventional connection devices furthers the higher cost of conventional fiber optic connections relative to copper wires.
Other conventional fiber optic connections include devices formed with fiber-alignment grooves. An example of such devices is disclosed in U.S. patent application Ser. No. 08/664,039, filed on Jun. 13, 1996, titled "Optical Fiber Connector Using Fiber Spring Force and Alignment Groove". With such devices, optic fiber connections are made in the grooves, which are, for example, V-shaped grooves. Ends of optic fibers to be connected are placed into the groove, and each end progresses along the groove until the end face abuts an end face of another optic fiber end. Optic fibers in the grooves may be positioned for alignment, so that the end faces of the optic fibers are in contact, creating optical connections. The grooves may be formed, for example, by injection molding of common engineering thermoplastic materials using standard molding practices. Such molded components are typically less costly than the ferrule and sleeve components and provide other advantages.
In the molded connectors providing grooves for the fiber optic connection, precision for alignment of fiber core end faces is achieved by locating the fiber ends in the grooves with end faces of the fiber ends abutting. Additionally, force may be applied to each of the fiber ends, directed so that the abutting end faces are forced together. The force on the fiber ends may be achieved by bowing one of the fibers as it is pressed toward another fiber in the groove. The bow force on the fiber ends improves the end face to end face engagement and, thus, the optical characteristics of the connection. Bowing of the optic fiber in this manner also accounts for tolerances due to variation in molding or due to assembly and in-field installation of the connectors and, thereby, provides a range of acceptable positions along the groove for the fiber end face to end face engagement.
A disadvantage of bowing the optic fiber to achieve end face to end face engagement of optic fibers in a groove, for example, a V-shaped groove, is that the bowing results in only a low magnitude force at the end to end junction of the fibers. This is because the particular force is limited to the extent of the bending stress of the bowed optic fiber. It would be an advantage to provide connectors that increase the magnitude of the force applied at the end to end junction of optical fibers connected in the groove.
Therefore what is needed is systems and methods for increasing the force applied at the end face junction of optical fibers connected in connectors having grooves. Embodiments of the present invention provide the increased junction force and maintain the benefits of using standard molded components. The invention overcomes many of the disadvantages and problems of the foregoing conventional techniques and devices.